A conventional sensor system for monitoring the operating parameters needed to determine the pressure in the intake manifold and the pressure seen by the exhaust gas recirculation (EGR) valve includes an absolute pressure sensor having a tap directly into the intake plenum to determine the manifold absolute pressure (MAP) and a separate sensor assembly for the EGR pressure. The EGR pressure sensor assembly typically includes an orifice mounted in an EGR tube just downstream of the location where the EGR tube taps into the exhaust stream, with pressure taps coming off of the EGR tube on both the upstream and the downstream side of the orifice. The two taps are connected to hoses that feed into a relative pressure sensor that compares the upstream and downstream pressures to obtain the delta pressure feedback exhaust (DPFE) signal. This signal is then used, along with the MAP and other signals to determine the valve opening for an EGR valve.
There are several drawbacks to this technique, however, in that there are two taps and two sets of hoses needed to obtain one DPFE pressure measurement, in addition to a separate MAP sensor. This then leads to the need for two separate sensor assemblies. Further, the location of the EGR taps and orifice, being close to where the EGR tube taps into the exhaust stream, are exposed to a great deal of heat, and so relatively expensive materials must be employed to withstand this heat and operate over the life of a vehicle. Further, during engine start-up in cold weather, these hoses can suffer from ice formation, creating limited EGR functioning.
Moreover, with these types of sensor configurations, there is no real option to run the pressure measurement lines through the housings of main engine components, so they must use separate hoses and connectors, creating more parts and more potential for reliability concerns.
Also of consideration for vehicles today is the desire to operate the fuel system as a returnless system. This generally requires a sensor at some point of the fuel system to measure the fuel pressure. This, then, along with the MAP and other signals are used to operate a fuel pump and the fuel injectors. However, this again adds more hoses and sensor assemblies to the overall sensor system, thus increasing cost and creating potential reliability concerns.
Consequently, an inexpensive, reliable and accurate sensing system is desired for use with internal combustion engines on vehicles.